Arachidonic acid activation of BKCa (Slo1)channel associated to β1 subunit in human vascular smooth muscle cells.

MARTIN, P; MONCADA, M; ENRIQUE, N; ASUAJE, A; VALDEZ CAPUCCINO, JM; GONZÁLEZ, C; MILESI, V

PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY

SPRINGER

Lugar: Berlin; Año: 2013 vol. 466 p. 1779 - 1792

0031-6768

Arachidonic acid (AA) is a polyunsaturated fatty acid (PUFA) involved in a complex network of cell signaling. It is well known that this fatty acid can directly modulate several cellular target structures, among them, ion channels. We explored the effects of AA on high conductance Ca2+- and voltage-dependent K+ channel (BKCa) in vascular smooth muscle cells (VSMCs) where the presence of β1-subunit was functionally demonstrated by lithocholic acid activation. Using patch-clamp technique, we show at the single channel level that 10 µM AA increases the open probability (Po) of BKCa channels 10-fold, mainly by a reduction of closed dwell times. AA also induces a left-shift in Po vs. voltage curves without modifying their steepness. Furthermore, AA accelerates the kinetics of the voltage channel activation by a 4-fold reduction in latencies to first channel opening. When AA was tested on BKCa channel expressed in HEK cells with or without the β1-subunit, activation only occurs in presence of the modulatory subunit. These results contribute to highlight the molecular mechanism of AA-dependent BKCa activation. We conclude that AA itself selectively activates the β1-associated BKCa channel destabilizing its closed state probably by interacting with the β1-subunit, without modifying the channel voltage sensitivity. Since BKCa channels physiologically contribute to regulation of VSMCs contractility and blood pressure, we used the whole-cell configuration to show that AA is able to activate these channels, inducing significant cell hyperpolarization that can lead to VSMCs relaxation.